NACA Duct Holes

Guys, I've noticed a lot of cars where the NACA duct holes are not cut out. I understand not doing this to keep out rain water, etc. but I'd like to suggest something I did on my center duct near the windscreen (my front ducts are cut out). I installed black contact paper (vinyl sticker material) where the hole should be. Nothing revolutionary, but I thought it should look like an open vent as on originals. I've had it on for over a year now and have had no lifting or peeling. Again, just a thought for others and as my good friend John Schneider and I say, "We're beautifying the world, one GT40 at a time."